Diphtheria toxoid lozenges were given to eighty-eight children aged 10–12 years who had previously been immunized by parenteral injection, and the antitoxin titres before and after administration were compared with those in a similar group of forty-six children who received formol toxoid by injection.

The results showed that a course of two lozenges at an interval of 1 week was a satisfactory means of reinforcing immunity in the children. The antitoxin response was less than that after injection, but a substantial response occurred in the children with low initial titres.

It is suggested that the lozenges might replace an injection as a means of reinforcing immunity in children aged 10–12 years and that they might be a valuable means of rapidly reinforcing the immunity of a large number of children in an epidemic.

The lozenges must be given under supervision to ensure that the children allow them to dissolve slowly in their mouths.

We should like to thank Dr J. D. Abbott of the Public Health Laboratory, Manchester, for separating the sera.

1. A model of anthrax infection in rhesus monkeys closely simulating human inhalation anthrax has been employed to study the course of the illness and methods of recognition and therapy.

2. Roentgenographic evidence of mediastinitis was detected early in the illness and served as a suitable indication for starting treatment.

3. Therapy with either penicillin or tetracycline appeared efficacious when started at the time chest roentgenograms first evidenced disease.

4. Isolation of penicillin-resistant B. anthracis from an animal dying during treatment with penicillin is reported.

Sera sent for routine examination from hospitals in south England and Wales were examined and compared with sera from the normal population. Choroiditis was the only disease syndrome showing a significantly higher proportion of positives than normal.

Cats were shown to be unlikely vectors of toxoplasma infection, at least by scratching.

Thanks are due to many pathologists throughout the country who sent sera and details of cases. Normal children's sera were kindly sent to me by Dr A. D. Evans of the Public Health Laboratory, Cardiff, Dr A. Macrae, Colindale, and Dr Margaret Wilson, Public Health Laboratory, Sheffield. Dr Patricia Bradstreet kindly sent me details of requests for cat scratch antigen.

Mr R. Payne carried out the dye tests and Mr H. J. Godwin of the Department of Pure Mathematics, University College of Swansea, kindly checked the statistical calculations.

Many thanks are due to Dr R. J. Drummond and his staff of the National Blood Transfusion Service (Welsh Region) for supplying the sera from blood donors.

The pH-stability of three strains of rinderpest virus, propagated in tissue cultures, was investigated at 4°C. in veronal-acetate buffers (Michaelis) of pH 3·0–10·7.

An attenuated laboratory strain, in its 95th culture passage (RBOK), showed maximal stability in the pH range 7·2–8·0, the half-life being about 3·7 days. It was relatively stable from pH 4·0 to 10·2, the half-life at the extremes of this range being over 2 hr. At pH 3·0 the infectivity declined very rapidly, the half-life period being 24·0 sec.

One virulent strain (RGK/1) showed a significantly lower resistance than strain RBOK at pH 3/0, probably also at pH 5·0. The inactivation rates for these two strains were, however, not greatly different at pH 10·7. The other virulent strain (RBT/1) was even less stable than RGK/1 at pH 4·0 or 5·0 but of a comparable stability at pH 9·0 and 10·2.

These findings are discussed in comparison with published data on the related viruses of measles and canine distemper. The importance of strain differences in studies of this kind is stressed.

We are grateful to Mr C. S. Rampton, A.I.M.L.T., and Mr L. W. Rowe, F.I.M.L.T., for help in the preparation of the diagrams. This paper is published with the permission of Mr H. R. Binns, C.M.G., O.B.E., Director, E.A.V.R.O.

During 1962, twenty-seven food poisoning incidents due to Salmonella typhimurium, phage type 4, comprising thirty-two cases and twelve symptomless excreters, occurred in the south-east Lancashire conurbation. The source of infection was a single small producer of English liquid egg. Pasteurization of the product coincided with the end of the outbreak. The cases were sporadic in distribution. Investigation of previous incidents due to this phage type in the City of Manchester pointed to egg from the same producer. As a result an investigation was made into the amount and source of unpasteurized egg in use in the city. This revealed the frequent presence of salmonella infection and demonstrated the need for pasteurization of liquid egg before use.

When trachoma and inclusion blennorrhoea viruses were titrated in chick embryo yolk sacs and the average day of death was plotted against dose of virus inoculated, sigmoid curves were obtained. Although all strains tested had the same growth rate, a given dose of some killed embryos more quickly than others. Strains killing most rapidly had the fewest elementary bodies per LD 50 and were the only strains to form inclusions in HeLa cells. During passage in the chick embryo three strains changed in their behaviour, killing embryos faster and acquiring the ability to form inclusions in HeLa cells.

We wish to thank our colleagues Miss D. M. Graham and Dr W. A. Blyth for allowing us to quote some of their observations and Dr L. H. Collier and Dr G. G. Meynell for their help and criticism.

Certain strains of Ps. aeruginosa produce, in addition to pyocines, substances which inhibit pyocine activity. These pyocine inhibitors are probably proteolytic enzymes.

In order to investigate the production of pyocines by various strains of Ps. aeruginosa, aeruginosa, nutrient agar medium was devised in which the action of the pyocine-inhibiting substances is suppressed by incorporating 10–5M iodoacetic acid, 0·1 % sodium citrate and 0·1 % dipotassium hydrogen phosphate. This medium also diminished slime production.

Pyocine production is a stable characteristic which is not lost on repeated sub-culture or prolonged storage, and might form the basis of a typing system for Ps. aeruginosa.

I wish to thank Dr M. T. Parker, Director of the Cross-Infection Reference Laboratory, Public Health Laboratory Service, for constant encouragement and helpful advice.

Presence of natural Cl. welchii α-antitoxin in 65 Indian equines was observed. All the 65 equines had 1 unit or more of circulating natural antitoxin per ml. of serum. The maximum titre observed was 4 units/ml. in about 8% of the animals. These figures are very much higher than the figures obtained in other countries. Such a high incidence of natural immunity indicates frequent natural contact with the antigen concerned.

Results of hyperimmunization of 7 equines are recorded and discussed.

Our thanks are due to the authorities of Bengal Immunity Laboratory for permission to publish these observations and to Sri M. Pal for useful technical assistance.

The PR8 strain of influenza virus can remain viable in ageing aerosols for considerable periods (Harper, 1961). However, viability of micro-organisms determined by their growth in vitro may not indicate their ability to infect animals via the respiratory route (Schlamm, 1960; Hood, 1961). If influenza is normally transmitted via this route it is epidemiologically important to establish whether any correlation exists between viability as measured by in vitro or in ovo methods and respiratory infectivity for a susceptible animal host. Previous reports on respiratory infectivity of aged influenza virus aerosols by Edward, Elford & Laidlaw (1943), Loosli, Lemon, Robertson & Appel (1943a) and Loosli, Robertson & Puck (1943b) lack such a comparison.

The number of bacteria on the hands of nurses using 2 % hexachlorophene soap intermittently was compared with the numbers of bacteria on the hands of nurses using ordinary soap. No significant differences were observed.

This study would not have been possible without the whole-hearted co-operation of the Matron, Miss M. Schurr, the Deputy Matron, Miss G. Davies and the Sisters and Nursing Staff of Fulham Hospital.

We are also indebted to Mr T. Ridgewell, Mr T. F. Fletcher and Miss Julia Fisher for technical assistance, and to Messers Bibby and Co. For their generous gift of soap.

Antigenic differences between the strains RV 11 and SA 13/61 of foot-and-mouth disease virus (type SAT 1) were studied in vivo by cross-protection tests. Cattle inoculated with formolized antigen of either strain developed good immunity to experimental infection with the identical strain but little resistance to the other strain.

In vitro the results of complement fixation tests and of serum-virus neutralization tests in tissue culture were consistent with the observations made in vivo. The results of studies on the serological relationships between four strains of type SAT 1 are presented.

The importance of strain differences in the epizootiology and control of the disease is discussed briefly.

The authors wish to thank Dr I. A. Galloway and Dr J. B. Brooksby for their advice and criticism, and to acknowledge the valuable technical assistance of Mr K. Herniman, Mr R. L. G. King and Mr E. Scoates.

More cells of Shigella sonnei were recovered on a chemically defined medium than on complex media after the cells were irradiated with ultraviolet light. The temperature of incubation affected the numbers of colony-forming cells that could be recovered. A temperature of 37° C. yielded the largest number of colonies compared with temperature of 15, 27 and 44° C. Recovery of irradiated cells was favoured when the cells were held in buffer at 25° C. for 2½ hr. before plating on solid media.

If Rift Valley fever virus (RVF), of which the main component has a sedimentation constant (S20) of about 450, is centrifuged under conditions adequate to secli ment MEF1 poliomyelitis virus (S20 = 156) completely, about 1 % of the original infective particles remain in the supernatant fluid. This slowly sedimenting (S10W) fraction was shown by centrifugation to contain infective components ranging in sedimentation constant from 4 to 19 Svedberg units. Density gradient centrifu gation showed that the densities of these particles varied from 1 to < 1 g./cm. The components were neutralized by RVF immune serum but were not affected by ribonuclease or deoxyribonuclease. In gel diffusion-filtration experiments the S10W virus behaved as substances having very low diffusion constants. Its filtration end-point using graded collodion membranes, is approximately two to three times higher than the ‘whole’ virus. It is suggested that particles comprising the S10W virus fraction contain lipoid material and may be filamentous.

The authors wish to express their gratitude to Prof. A. Kipps and R. A. Alexander for their continued interest in this work and to Dr T. H. Mead for many helpful suggestions during preparation of the manuscript.

This investigation was supported in part by a Public Health Service research grant Al 04044–02 from the National Institute of Health, Bethesda, U.S.A.

1. In two hospitals, post-operative staphylococcal wound sepsis occurred with equal frequency in patients who were and in those who were not nasal carriers of Staph. aureus.

2. Nasal carriage of Staph. aureus was not always associated with skin carriage at the site of operation, but even patients who were skin carriers suffered no more sepsis than non-carriers.

3. Self-infection was a less frequent cause of sepsis than was cross-infection. Other investigations of this type have revealed conflicting findings on the frequency of self-infection. These may be due to differences in the epidemiological properties of staphylococci infesting the hospitals; to different methods of preoperative skin preparation; and to the different types of operation concerned.

4. In one of the hospitals, 31% of probable operating-room infections were with organisms similar to those carried by some member of the surgical team. In infections thought to have occurred in the ward, only 10% showed this similarity. In 11 of 35 presumed operating-room infections, the source may have been a member of the surgical team.

For help and co-operation we are grateful to Mr G. A. Mason, Senior Surgeon, Newcastle Regional Thoracic Surgery Service; and Dr Joan Millar, Miss G. Jones, Miss E. Smith, Mrs Jean Best, Miss Winifred Mahon, Dr K. Hodgkin, Dr W. Stewart, Mr S. Griffin, Mr W. C. Barnsley, Mr R. Dobson, Mr W. H. Bound, and many nurses and other hospital workers. Our especial thanks are due to Professor R. E. O. Williams, who phage-typed many of the staphylococci, and then taught us to do this for ourselves.

Suspensions of FMD virus treated with 0·05% formalin at 26° C. for periods up to 144 hr. remained infective for cattle, although the infectivity could not be detected in the presence of aluminium hydroxide. Infectivity was detected in similar virus suspensions which had been treated with 0·05% AEI at 37° C. for 8 hr. but not in suspensions treated for 12 hr.

Vaccines prepared from these suspensions were antigenically potent and serum neutralization tests demonstrated the development and regression of serum antibody. The AEI vaccines were at least as potent as the corresponding formalin vaccines.

An analysis has been made of the records of 5290 attendances at the Common Cold Research Unit, Salisbury, during the years 1946 to 1957. Materials prepared from the nasal washings of persons suffering from colds were administered to 993 volunteers, of whom 386 (38·9 %) showed definite evidence of infection within a few days. The attack rate of these experimentally induced colds was lower during the months October to March than from April to September. The difference was statistically significant as regards male but not as regards female volunteers.

Six strains of virus were propagated by passage from volunteer to volunteer, in one instance up to the eighth serial transfer from the original material, without apparent loss of pathogenic properties. Comparison of the clinical effects of these strains, and of a number of miscellaneous strains, revealed several differences which were minor in character but, statistically, highly significant. These comprised differences in attack rate, severity, incubation period, duration and relative frequency of symptoms, which could not be ascribed to seasonal or other influences.

It was concluded that the observed variations in the clinical pattern of the experimentally induced colds were attributable to qualitative differences in the strains of virus used.

I wish to thank Sir Christopher Andrewes, F.R.S., for his unfailing help and encouragement at every stage of this investigation and all my colleagues at the Common Cold Research Unit for much useful comment and discussion. I am indebted to the Statistics Department of the Ministry of Labour and National Service for processing the records and to Mr R. G. Carpenter for assistance with some of the statistical analyses.

1. A survey of post-operative wound infection was done in 1959–60 on 559 surgical patients admitted to a provincial general hospital.

2. Clinical evidence of post-operative wound sepsis was observed in 71(12·7 %), suppuration in 51(9·1 %) and staphyloccocal wound sepsis in 48 (8·6 %).

3. Seventeen of the patients died in hospital. Although 5 of these had septic wounds, the sepsis did not appear to have been the cause of death.

4. Contrary to some reported findings, the post-operative wound sepsis rate was considerably lower in patients who were staphylococcal nasal carriers on admission to hospital than in non-carriers. Nine out of 153 carriers (5·9 %) developed wound sepsis and 36 out of 385 non-carriers (9·4 %). When allowance is made for 3 highly probable self-infections, the incidence of wound cross-infection was 3 % in carriers and 9 % in non-carriers.

5. The excess of sepsis in non-carriers could not be explained in terms of different age or sex distribution in carrier and non-carrier groups, nor by differences in the types of operation undergone or in degree of exposure to staphylococcal contamination.

6. The excess of sepsis in non-carriers was accounted for by the patients whose wounds had drains rather than by clean-stitched wounds.

7. Those carriers who harboured a staphylococcus of the 80/81 group in the nose on admission to hospital had a higher incidence of wound sepsis than carriers of other phage types or staphylococcus.

8. Three probable instances of wound self-infection occurred, and in the early stages of the survey at least 5 wound infections were probably directly caused by two members of the theatre staff carrying staphylococci of the 80/81 group in the nose and with existing skin sepsis or a recent history.

9. The survey findings and a study of the literature suggested: (a) that the acquisition of a nasal staphylococcus in hospital was probably, as a rule, evidence of exposure to staphylococeal contamination and not a determinant of wound sepsis, unless the patient also became a skin carrier; (b) that a small proportion of patients are self-infected, some are directly infected by theatre personnel, and the wounds of other patients are directly or indirectly contaminated by staphylococci from the ward environment; (c) that wool or cotton fluff contaminated with staphyloccoci may cause wound sepsis by falling into open wounds and as foreign bodies induce a significant reduction in the minimum pus-forming dose of staphylococci; (d) that before ascribing high or low sepsis rates to factors such as the nasal carrier state, the relevant groups should be shown not to differ materially in respect of other factors known to influence the incidence of wound sepsis.

We gratefully acknowledge the help and encouragement of our surgical colleagues Mr H. P. Guerrier, Mr P. J. W. Monks, Mr J. Macpherson and Mr C. C. Jeffery; and of Dr C. P. Warren, consultant pathologist to the Torbay Hospital, Mrs M. Stamp, Matron, Sister E. M. Cottrell, first Infection Control Sister at the Torbay Hospital, and her successor Mr H. Street.

Acknowledgement is also due to the South Western Regional Hospital Board for its encouragement and for a research grant for technical aid, without which the surveys described would not have been possible.

Inactivated vaccines have been prepared from one strain of FMD virus grown in guinea-pig pad epithelium, unweaned mice and cultured pig kidney and baby hamster kidney cells. The potencies of these vaccines in protecting guinea-pigs against challenge with inoculated infective virus of the same strain have been compared and related to the amounts of 25 mμ component present in the different virus suspensions. Although it was possible to obtain a relationship between the content of 25 mμ component and potency for an individual source of virus, this relationship does not hold for all the different sources of virus used. It is suggested that the reason for this failure is the partial masking of the 25 mμ component by a cell constituent present in some of the virus suspensions so that the component is incompletely estimated by the complement-fixation test.

H.influenzae type b, the sero-type which causes meningitis, was isolated from 3 (2·4 %) of 127 naso-pharyngeal swabs from white non-Jamaican children resident in Jamaica, and from 14 (2·9 %) of 473 such swabs from a mixed group of Jamaican children. Much higher frequencies were found in households in which cases of haemophilus meningitis had recently occurred (41 %), in the nursery of an orphan home (up to 70%) and in a day-nursery. In the orphan home nursery the high frequency persisted over a number of months, but no case of meningitis or other relevant disease occurred. A high concentration of this organism is therefore compatible with normal health, and the significance of high concentrations in the homes of meningitis patients is not certain.

I am indebted to the Standing Advisory Committee for Medical Research in the British Caribbean for a grant towards the cost of materials; to a number of colleagues at the University College of the West Indies, notably Dr E. H. Back, Senior Lecturer in Paediatrics, and the staff of the Department of Social and Preventive Medicine; to those in charge of the orphan home, the day-nursery, the play-school and the other institutions visited; to many cooperative parents and children and to my wife for help in the collection of specimens.

Twenty-three strains of rhinovirus were isolated from 102 patients who had common colds on arrival at a Royal Air Force recruit centre during a 6-month period from June to November, 1960. Three of these strains were M type rhino-viruses similar to ECHO 28 virus. Twenty strains were H type rhinoviruses which fell into six or more different antigenic types. Two of these types were similar to the prototypes Sal/1/58/H and Sheffield/1/60/H. Three types were antigenically distinct from those previously reported in this country and several strains are still unclassified. Other human respiratory viruses were not isolated from common colds occurring at this time among the population studied.

We are indebted to the Senior Medical Officer of R.A.F. Cardington for providing facilities for the investigation, to Squadron Leader M. Shearer for his help in collecting convalescent blood specimens, and to the Director-General of the Royal Air Force Medical Service for permission to publish this paper.

We wish to acknowledge the excellent technical assistance of Miss Ann Deacon. We should also like to thank Dr H. E. M. Kay of the Royal Marsden Hospital for supplying human embryo kidney.